Dilatation of the base of the heart occurs with various diseases of the heart and often is a causative mechanism of heart failure. In some instances, depending on the cause, the dilatation may be localized to one portion of the base of the heart (e.g., mitral insufficiency as a consequence of a heart attack affecting the inferior and basal wall of the left ventricle of the heart), thereby affecting the valve in that region. In other cases, such as cardiomyopathy, the condition may be global affecting more of the heart and its base, causing leakage of particularly the mitral and tricuspid valves. Other conditions exist where the mitral valve structure is abnormal, predisposing to leakage and progressive dilatation of the valve annulus (area of valve attachment to the heart). This reduces the amount of blood being pumped out by the ventricles of the heart, thereby impairing cardiac function further.
In patients with heart failure and severe mitral insufficiency, good results have been achieved by aggressively repairing mitral and/or tricuspid valves directly, which requires open-heart surgery (Bolling, et al). The mitral valve annulus is reinforced internally by a variety of prosthetic rings (Duran Ring, Medtronic Inc) or bands (Cosgrove-Edwards Annuloplasty Band, Edwards Lifesciences Inc). The present paradigm of mitral valve reconstruction is therefore repair from inside the heart, with the annulus being buttressed or reinforced by the implantation of a prosthetic band or ring. Since this is major open-heart surgery with intra-cavitary reconstruction, there is the attendant risk of complications and death associated with mitral valve surgery. Another approach has been to replace the mitral valve, which while addressing the problem, also requires open-heart surgery and involves implantation of a bulky artificial, prosthetic valve with all its consequences. Because every decision to perform major surgery requires some risk vs. benefit consideration, patients get referred for risky surgery only when they are significantly symptomatic or their mitral valve is leaking severely.
In contrast to the more invasive approaches discussed above, in specific instances of inferior left ventricular wall scarring causing mitral regurgitation, Liel-Cohen and co-workers have suggested localized pressure or support of the bulging scar of the inferior wall of the heart from the outside (Liel-Cohen. N. et al. (2000) “Design of a new surgical approach for ventricular remodeling to relieve ischemic mitral regurgitation: insights from 3-dimensional echocardiography”. Circulation 101 (23):2756-2763).
Another less invasive approach to preventing global heart dilation is ventricular containment with a custom made polyester mesh, or cardiac support device (U.S. Pat. Nos. 6,077,218 and 6,123,662). These devices are designed to provide a passive constraint around both ventricles of the heart, and constrain diastolic expansion of the heart. Other devices include ventricular assist devices that provide cardiac assistance during systole and dynamic ventricular reduction devices that actively reduce the size of the heart. However, this technique does not specifically address valve leakage using a device that reinforces the base of the heart in all phases of the cardiac cycle.
Percutaneous approaches (including “edge-to-edge”, placating the annulus and coronary sinus approaches) of accessing the heart through the femoral artery have been used. Disadvantages of percutaneous approaches include fixture-made-clots being sent downstream, and the dangers of potential patient allergy to contrast media. In addition, percutaneous approaches require complicated systems and are very dependent on the anatomy of the patient. As a result these systems require the help of an experienced and trained interventional cardiologist to assist with the procedure.
An example of a system that provides a less invasive approach to base stabilization is found in U.S. Pat. No. 6,716,158 to Raman et. al. However, although the Raman et. al. system operates to stabilize the base of the heart, it does not provide a system to modulate or modify heart valve function by applying localized pressure to particular regions of the heart, for example, to tissues adjacent to heart valve. Such a system would advantageously apply inward pressure to tissue adjacent to the heart valves so as to modify the shape or reduce the size of a heart valve itself. Accordingly, there is a need to non-invasively repair or re-configure the shape of a mitral and/or tricuspid valve so as to treat valve dilation and resulting valve insufficiency problems.
The present invention is directed to solving the above mentioned problems and can advantageously be applied to both patient populations requiring heart valve modification by applying localized pressure, and to patient populations simply requiring external stabilization of the base of the heart.